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CIRIA
Classic House, 174–180 Old Street, London EC1V 9BP, UK
TEL +44 (0)20 7549 3300 FAX +44 (0)20 7253 0523
EMAIL enquires@ciria.org
Standards for the repair of buildings following flooding
Garvin, S; Reid, J; Scott, M
CIRIA
CIRIA publication C623 © CIRIA 2005 ISBN 0-86017-623-1 RP676
British Library Cataloguing in Publication Data
A catalogue record is available for this book from the British Library.
Published by CIRIA, Classic House, 174–180 Old Street, London EC1V 9BP, UK. All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, including photocopying and recording, without the written permission of the copyright-holder, application for which should be addressed to the publisher. Such written permission must also be obtained before any part of this publication is stored in a retrieval system of any nature.
This publication is designed to provide accurate authoritative information in regard to the subject matter covered. It is sold and/or distributed with the understanding that neither the authors nor the publisher are thereby engaged in rendering a specific legal or any other professional service. While every effort has been made to ensure the accuracy and completeness of the publication, no warranty or fitness is provided or implied, and the authors and publisher shall have neither liability nor responsibility to any person or entity with respect to any loss or damage arising from its use.
Keywords
Concrete and structures, design and buildability, flooding, housing, materials, refurbishment, sustainable construction
Reader interest Owner/occupiers, insurers, developers, builders, construction clients Classification AVAILABILITY CONTENT STATUS USER Unrestricted Advice/guidance Committee-guided Owner/occupiers, insurers, developers, builders, construction clients
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Flooding is a major problem for many people in the United Kingdom, posing a risk to health, safety and wellbeing, and resulting in widespread damage to property. The scale of the problem can be gauged from the following quotation (OST, 2004):
Nearly 2 million properties in floodplains along rivers, estuaries and coasts in the UK are potentially at risk of flooding. 80,000 properties are at risk in towns and cities from flood-ing caused by heavy downpours that overwhelm urban drains – so-called ‘intra-urban’ flooding. In England and Wales alone, over 4 million people and properties valued at over £200 billion are at risk.
In the autumn 2000 floods, 10 000 properties were flooded at more than 700 locations at a cost in the order of £1.0 billion.
With the effects of climate change and increased societal pressures on the country’s infrastructure and services, the risks of flooding are predicted to increase considerably. Flood damage to properties can range from minor effects on walls, floors, basements and services to serious structural damage to buildings. However, practical steps can be taken to reduce the cost of flood damage and to speed up recovery times should the flood return.
This guide sets out requirements for the repair of buildings following flooding and includes:
a description of the causes of flooding and the impact that floods can have on buildings
making safe, decontamination and drying activities that must be undertaken immediately after the floodwaters have receded, including recommendations on appropriate health and safety risk assessments
conducting post-flood surveys and future flood risk assessments standards of repair for buildings following flooding.
The repair of buildings has to be appropriate to both the extent of damage and the risk of future flood. As the risk increases the proposed standard of repair is more rigorous, effectively increasing the resilience or resistance of the building to flooding. Three levels of standards of repair are included in the guidance. For each standard of repair, guidance is provided for external walls, internal walls, floors, fenestration, basements, services and fittings.
The guide contains illustrations of damage, surveys, drying and decontamination, and repair work to buildings. Appendices include guidance to homeowners, technical information, key organisations that can advise on flooding and information on the provision of insurance.
The guidance is aimed primarily at building professionals and insurers experienced in flood damage and repair. It may also be used by general builders, surveyors and building-owners, including householders, for advice in commissioning repair work.
Acknowledgements
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Reesseeaarrcchh ccoonnttrraaccttoorr This book is the result of CIRIA Research Project 676 “Standards for the repair of buildings following flooding”. The report was prepared by BRE Scotland.
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Auutthhoorrss Stephen Garvin BSc PhD, of BRE Scotland
As director of BRE Scotland Stephen is responsible for research into the impact of climate and moisture on buildings. He has led research projects on durability of materials in severe climates and the impact of climate change on construction. He is involved in European networks on flooding and the impact of climate change on flood risk to buildings.
John Reid BSc, of BRE Scotland
A principal consultant at BRE Scotland, John is responsible for construction technology and process. He is mainly concerned with building defects, failure and remedial measures.
Marianne Scott BSc MSc, independent consultant
Previously a research manager at CIRIA, Marianne works on water-related research projects with a flooding, coastal and marine focus.
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Otthheerr ccoonnttrriibbuuttoorrss CIRIA would also like to acknowledge the contribution of the project team, in particular:
Craig Elliott CIRIA
Martin McCreadie formerly BRE Scotland
Peter Trotman BRE
Chris Sanders Glasgow Caledonian University (formerly BRE)
Mark Phillipson Glasgow Caledonian University (formerly BRE)
Mike Waterfield British Damage Management Association.
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Stteeeerriinngg ggrroouupp Following CIRIA’s usual practice, the research project was guided by a steering group, which comprised:
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Chhaaiirr John Blanksby University of Sheffield
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Atttteennddiinngg mmeemmbbeerrss Jason Bingham Davis Langdon (DTI)
Pam Bowker HR Wallingford Ltd
Chris Broadbent BRE
Nathalie Carter House Builders Federation
Jonathan Chapman Environment Agency
Tony Clack CILA
Gill Holland National Flood Forum
Mike Johnson Office of the Deputy Prime Minister
Jim Millmore ICE Water Board, Babtie Group Ltd
Christopher Mills NHBC
Andrew Petfield RICS
Eddie Roberts Flood Protection Association
Keith Snook RIBA
Roy Stokes Environment Agency
Mike Waterfield British Damage Management Association
John Wickham Norwich Union
David Wilkes Severn Trent Water Ltd.
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Coorrrreessppoonnddiinngg Jackie Bennett Council of Mortgage Lenders m
meemmbbeerrss Mervyn Bramley Environment Agency
Catherine Bond House Builders Federation
Karen Carr Defra
Sebastian Catovsky ABI
David Crichton Crichton Associates
Christine Ecob Environment Agency
Rob Jarman National Trust
Barry Layen Lewes District Council
Jim Leat Atkins
Fiona McKenzie Scottish Executive
Brian Ridout English Heritage
Paul Ryles SEPA.
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CIIRRIIAA mmaannaaggeerrss CIRIA’s research managers for the project were Marianne Scott, Craig Elliott and
Elizabeth Holliday.
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Prroojjeecctt ffuunnddeerrss The project was funded by:
DTI
Defra/Environment Agency joint flood and coastal management R&D programme British Damage Management Association (BDMA).
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Phhoottooggrraapphhss The following organisations are thanked for their provision of photographic material: Building Research Establishment
CIRIA Flood Ark Ltd Floodguard International Ltd Geodesign Barriers Ltd Hydroscience Ltd Safeguard Chemicals Ltd Sto Limited
WA Fairhurst & Partners.
Neither CIRIA nor the authors of this book endorse the products or manufacturers illustrated in the photographs.
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Coonnttrriibbuuttoorrss CIRIA and the authors are grateful for the help given to this project by the funders, the members of the steering group, and by the many individuals who were consulted and provided data. In particular, acknowledgement is given to the following:
Peter Bullivant Isothane Ltd
Peter Chilvers LABC Services
Tom Crossett Lewes Flood Action
Douglas Kent SPAB
David Stirling Arup
Chris Griffith-Jones Winchester City Council
John Purser Dallmer Ltd
Kieran Williams Thames Water
Fola Ogunyoye Posford Haskoning
Peter Watt Brick Development Association
Glyn Woodward Floodskirt Ltd
Gerry Pettit Concrete Block Association.
The project team would also like to thank all those that attended the consultation workshop.
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Summary . . . 3
Acknowledgements . . . 4
List of figures, tables and boxes . . . 9
Glossary and acronyms . . . 10
Reader guide – where to find information in this book . . . 12
1 Introduction . . . 13
1.1 Flooding – sources and implications . . . 13
1.2 Standards of repair. . . 16
1.3 Flood repair roles and responsibilities. . . 16
1.4 About this guide . . . 17
1.5 Related guidance . . . 19
2 Making safe, decontamination and drying . . . 21
2.1 Making safe . . . 21
2.2 Decontamination . . . 26
2.3 Drying . . . 29
3 Post-flood survey and reducing the impacts of future floods . . . 39
3.1 Post-flood survey. . . 39
3.2 Reducing the impacts of future flooding. . . 47
3.3 Insurance . . . 54
4 Standards of repair. . . 57
4.1 Standards of repair: overview . . . 58
4.2 Flood protection measures. . . 60
4.3 Standards of repair for external masonry . . . 62
4.4 Standards of repair for the outer face of external walls . . . 63
4.5 Standards of repair for the internal face of external walls . . . 70
4.6 Standards of repair for wall cavities. . . 73
4.7 Standards of repair for rising damp in masonry walls . . . 75
4.8 Standards of repair for internal walls and partitions . . . 76
4.9 Standards of repair for fenestration . . . 80
4.10 Standards of repair for solid floors . . . 83
4.11 Standards of repair for suspended concrete floors . . . 86
4.12 Standards of repair for floating floors . . . 87
4.13 Standards of repair for suspended timber floors . . . 88
4.14 Standards of repair: other floor issues. . . 90
4.15 Standards of repair for services . . . 91
4.16 Standards of repair for fittings. . . 93
4.17 Standards of repair for basements . . . 94
Appendices . . . 100
A1 Organisations that can advise on flooding . . . 101
A2 Example risk assessment . . . 105
A3 Advice for building-owners . . . 109
A3.1 Making an insurance claim . . . 109
A3.2 Appointing a surveyor . . . 110
A3.3 Appointing repair contractors . . . 110
A4 Guidance on dehumidification . . . 111
A4.1 Types of dehumidifier . . . 111
A4.2 Dehumidification using the refrigeration principle . . . 111
A4.3 Dehumidification using the desiccant principle . . . 111
A4.4 Frequently asked questions . . . 112
A5 Floor finishes . . . 115
A5.1 Jointless floor finishes. . . 115
A5.2 Jointed finishes . . . 116
A5.3 Jointed hard finishes . . . 117
A5.4 Timber and timber products . . . 118
A6 ABI statement of principles on the provision of flooding insurance . . . 119
A7 A simple example of whole-life costing . . . 121
A8 References. . . 123
A8.1 General . . . 123
A8.2 British Standards . . . 125
A8.3 BRE publications by series . . . 128
A8.4 CIRIA publications by series . . . 129
A9 Further reading . . . 130
A9.1 General . . . 130
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1.1 Flood entry routes into a house . . . 14
1.2 Structural flood damage . . . 15
1.3 Recommended repair process for a flooded building . . . 20
2.1 Method for safe and effective decontamination and drying of a flooded building . . . 22
2.2 Floor boards damaged and removed to allow for surveying. . . 26
2.3 Flood damage to walls. . . 28
2.4 Removed plasterboard . . . 28
3.1 Post-flood survey and reducing the impacts of future floods process. . . 40
3.2 Flood-damaged floors . . . 42
3.3 Flood damage to plaster . . . 43
3.4 Risk assessment procedure to determine level of repair required for the flooded building . . . 55
4.1 Specification for the standard of repair for building elements of flooded buildings . . . 58
4.2 Air brick cover . . . 61
4.3 Flood door board . . . 61
4.4 Render application . . . 64
4.5 Basement tanking – internal membrane application . . . 69
4.6 Pallet barrier . . . 96
4.7 Flood door board . . . 97
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2.1 Direct and indirect health effects . . . 252.2 Decontamination and drying for different building elements . . . 36
3.1 Post-flood survey checklist for external wall elements. . . 42
3.2 Post-flood survey checklist for internal wall elements . . . 43
3.3 Post-flood checklist for floor elements . . . 44
3.4 Post-flood checklist for basements and cellars . . . 45
3.5 Post-flood checklist for services. . . 46
3.6 Post-flood checklist for fixtures and fittings . . . 47
4.1 Particular flood damage vulnerability of typical construction elements . . . 59
4.2 Moisture penetration and waterproofing of external masonry. . . 62
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3.1 Factors to be considered to help determine the likelihood of a future flood . . . . 503.2 Factors to be considered to help determine the consequences of a future flood . 51 4.1 Contents of Chapter 4. . . 57
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Cadw Welsh Historic Environment Agency, an organisation within the Welsh Assembly. The
Welsh word cadw means “to keep”.
Contamination Characteristic of matter that has an adverse effect on the quality of materials or surfaces,
including solid or liquid deposits left after a flood. These may contain pollutants and hazardous substances, which should be removed as part of the remedial process.
Damp-proof course Layer or coating of material covering the bedding surface of a masonry wall to resist
(DPC) the passage of moisture. It will prevent groundwater rising up into the building,
com-monly known as rising damp.
Damp-proof Layer or sheet of material within a floor or similar construction or vertically within a
membrane (DPM) wall to prevent passage of moisture. A damp-proof membrane is similar to a DPC, but
may be used in solid ground floors to prevent rising damp. To be fully effective, it should be connected to both the DPC in surrounding walls and any basement tanking.
Defra Department for the Environment, Food and Rural Affairs.
Dehumidification Removal of water from the air using an appropriate commercial device. This process
can promote drying of the building, but must be controlled to avoid over-drying of the structure.
DoENI Department of the Environment, Northern Ireland.
Dry-proofing Applying measures to the outside of a building to prevent floodwater from penetrating
into the structure. This may include a mixture of measures to improve the flood resistance of the floors and walls of the structure and can include flood barriers, drainage systems and flood protection products, or methods such as repointing masonry or raising floor levels.
Fenestration External elements of a building comprising windows, doors, glazing and hardware.
Flash flooding Rapid flooding caused by overland flows. This is generally caused by excessive rainfall
running off impermeable surfaces at a rate that exceeds the capacity of the local drainage infrastructure.
Flood protection For the purposes of this guide this is the use of barriers and drainage infrastructure to
reduce the risk of floodwater affecting a building. It can include the use of proprietary flood protection products, but also may include larger civil engineering works.
Flood risk assessment For the purposes of this guide, a distinction is made between the future flood risk
assessment of a building and the health and safety risk assessment. The flood risk assessment considers the nature of the hazard, the type of floodwater, the likelihood of return and the duration and depth of the flood. The health and safety risk assessment considers requirements for the making safe, decontamination and drying of the building.
Flood skirt A flood protection system designed to wrap around a property to a maximum depth of
1 m above ground level. It provides temporary protection to the external faces of the building, preventing floodwater from seeping through the building fabric as well as through openings.
Groundwater flooding Flooding caused by water contained in the ground rising to the surface. This water can
Intermittent stream In English geology, a river that is usually dry in the summer months. Also known as a winterbourne or ephemeral stream.
Permeability Characteristic of a material that determines the rate at which liquids pass through it.
For the purposes of this guide, this includes moisture passing through materials using cracks, capillaries and absorption processes.
Relative humidity The ratio of water vapour pressure in the air at a given temperature to the saturation
vapour pressure at the same temperature; commonly expressed as a percentage.
Resilience to flood For the purposes of this guide, a characteristic of a building material, component or
whole building that describes its ability to recover from flooding.
Resistance to flood For the purposes of this guide, a characteristic of a building material, component or
whole building that enables it to remain undamaged and unaffected by floodwater.
Risk assessment For the purposes of this guide, the process of identifying and assessing the hazards to
(health and safety) health and safety of those involved during the post-flood work (decontamination,
drying, surveys and repairs). Hazards can include the structural safety of the building or risks from water-borne diseases.
Risk assessment For the purposes of this guide, risk is equal to the product of the likelihood (the chance
(future building flood) of a flood occurring) and consequences (the amount of damage to a building) of a future
flood.
Standard of repair The extent to which repair work is carried out and the extent of measures undertaken
(SoR) so that damage from future flooding is minimised. Standards of repair are determined
through risk assessment. The resilience and resistance measures in the standard of repair include dry-proofing and wet-proofing of the property.
Tanking Impervious membrane used to prevent the infiltration of subsurface water; usually
associated with basement walls and floor below, or close to, the water table.
Visqueen A sticky, rubbery, waterproof material that is applied directly to a structure as a
waterproofing measure.
Wet-proofing For the purposes of this guide, the replacement of water-vulnerable elements in the
building with water-resistant alternatives so that future flooding causes less damage.
Whole-life costing A methodology used to assess the cost performance of construction work, aimed at
(WLC) facilitating choices where there are alternative means of achieving the client’s objectives
and where those alternatives differ, not only in their initial costs but also in their durability and subsequent operational costs.
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A Appppeennddiixx 99 F
Fuurrtthheerr rreeaaddiinngg
List of relevant British Standards and additional references A Appppeennddiixx 88 R Reeffeerreenncceess Key references and sources of information for flooding and associated issues A Appppeennddiixx 77 A
A ssiimmppllee eexxaammppllee o
off wwhhoollee--lliiffee c coossttiinngg
A comparison of the relative costs incurred for different standards of repair and how this can support decision-making A
Appppeennddiixx 66 A
ABBII ssttaatteemmeenntt ooff p
prriinncciipplleess
A description of the Association of British Insurers’ (ABI) principles and policy on flood insurance and its availability A
Appppeennddiixx 55 F Flloooorr ffiinniisshheess
Description of common construction forms Comment on flood resilience measures for each construction form A Appppeennddiixx 44 G Guuiiddaannccee oonn d
deehhuummiiddiiffiiccaattiioonn
Important information on the process of dehumidifying a previously flooded building Frequently asked questions A Appppeennddiixx 33 A
Addvviiccee ffoorr bbuuiillddiinngg o owwnneerrss Relevant advice for making an insurance claim and appointing surveyors and repair contractors A Appppeennddiixx 22 E Exxaammppllee rriisskk a asssseessssmmeenntt
An example of a risk assessment approach to the future flood risk of a building. Flood risk assessment is essential in determining an appropriate standard of repair A Appppeennddiixx 11 O
Orrggaanniissaattiioonnss tthhaatt c caann aaddvviissee oonn ffllooooddiinngg Contact details of relevant organisations that can help when flooding occurs C
Chhaapptteerr 44 S Sttaannddaarrddss ooff rreeppaaiirr ((SSooRR))
Specification for the SoR for
external masonry external walls wall cavities rising damp in masonry walls internal walls and partitions fenestration floors services fittings basements Flood protection products available Purpose of a flood repair log C Chhaapptteerr 33 P
Poosstt--fflloooodd ssuurrvveeyy a
anndd rreedduucciinngg tthhee iimmppaaccttss ooff ffuuttuurree ffllooooddss Advice on undertaking post-flood survey of damage to the building Guidance on assessing risk, including the likelihood of future folds and the potential consequences of a flood event Identifying appropriate standards of repair (SoR) required for a building C Chhaapptteerr 22 M Maakkiinngg ssaaffee,, d
deeccoonnttaammiinnaattiioonn a
anndd ddrryyiinngg
Making safe a building including health and safety concerns Recommended procedures for decontaminating a building Advice for the process of drying a building Summary of both activities relevant to specific building elements F Foorr rreeaaddeerrss u
unnffaammiilliiaarr wwiitthh fflloooodd pprroobblleemmss
F Foorr p prraaccttiittiioonneerrss
C Chhaapptteerr 11 IInnttrroodduuccttiioonn
Problems posed by flooding to people living in the United Kingdom Flood sources and implications Scope of the guide How to use the guide Intended users Roles and responsibilities Related CIRIA guidance
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Flooding is a major problem for many people in the United Kingdom, posing a risk to health, safety and wellbeing, resulting in widespread damage to property. The scale of the problem can be gauged from the following quotes (OST, 2004):
Nearly 2 million properties in floodplains along rivers, estuaries and coasts in the UK are potentially at risk of flooding.
80,000 properties are at risk in towns and cities from flooding caused by heavy downpours that overwhelm urban drains – so-called “intra-urban” flooding.
In England and Wales alone, over 4 million people and properties valued at over £200 billion are at risk.
Each year… we experience an average of £1,400 million of damage.
In the autumn 2000 floods, 10 000 properties were flooded at more than 700 locations at a cost of about £1.0 billion.
More than 5 per cent of the population of the UK live in areas that are less than 5 m above mean sea level, including parts of London and other major cities.
Thousands of people have suffered trauma and damage to homes and valuables. Research commissioned by the insurance industry has shown that for a flood 1 m deep, the average cost of the loss of buildings is £22 000 and of contents £13 000, although they can be much higher (Black and Evans, 1999). The potential effects of climate change and societal pressures to increase development in “at risk” areas make it likely that the risks of flooding will increase considerably. However, practical steps can be taken to reduce the cost of flood damage and to speed up recovery times.
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Flooding can occur as a result of any of the following (ODPM, 2001; CIRIA and EA, 2003):
flooding from watercourses such as rivers and streams, associated with extreme rainfall, snowmelt or hail, or overtopping of river defences
surface water runoff
the sea, through overtopping of sea defences groundwater rising into buildings
infrastructure failure
blocked or overloaded stormwater drainage systems and sewer flooding ducts used for service main inlets, particularly water mains
accidental escape or leakage from household appliances such as radiators, dish washers etc.*
* Accidental escape or leakage from household appliances is outside the scope of this guide, although some of the principles of repair discussed herein may still apply.
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Buildings will allow water to enter during a flood through (see Figure 1.1):
masonry and mortar joints where the natural permeability of both these materials, particularly the mortar, can be high
the brickwork/blockwork cracks in external walls
vents, airbricks and flaws in the wall construction
or around windows and doors at vulnerable points such as gaps and cracks in the connection of the frames and walls
door thresholds especially where these have been lowered to the ground to allow level access
gaps around wall outlets and voids for services such as pipes for water and gas, ventilation for heating systems, cables for electricity and telephone lines
party walls of terraced or semi-detached buildings in situations where the property next door is flooded
the damp-proof course, where the lap between the wall damp-proof course and floor membrane is inadequate
sanitary appliances (particularly WCs, baths and showers) caused by back-flow from flooded drainage systems.
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The amount of damage caused to buildings will depend, among other factors, upon the water depth of exposure, as follows.
1 Below ground floor. Basement damage, plus damage to any below-ground electrical
sockets or other services, carpets, fittings and possessions. Minimal damage to the main building. Deterioration of floors may result if the flood is of long duration, and/or where drying out is not effective.
2 Above ground floor. In addition to the above, damage to internal finishes, saturated
floors and walls, damp problems, chipboard flooring destroyed, plaster and plasterboard. Services, carpets, kitchen appliances, furniture, electrical goods and belongings are all likely to be damaged to the point of destruction. Services such as water tanks and above ground electrical and gas services may be damaged.
NOTE: if a flood event of greater than 1 m depth above floor level has been experienced
there may be additional factors that need to be considered before following the guidance in this publication (out of scope for this publication). Under no circumstances should flood protection products be used to a height of more than 1 m above ground floor level (see Section 1.4.3).
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The duration of the flood can make a significant difference to the extent of cleaning and repair that is required. Generally, short-duration flash flooding will be quickly remedied, and will be less costly to repair than a flood of longer duration. A flood lasting more than 24 hours can cause serious damage to the building elements (see Figure 1.2). The nature of the floodwater is also significant – for example, saltwater from coastal floods promotes corrosion to metal components, and water containing sewage requires extensive cleaning and decontamination.
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This guide provides detailed specifications for the repair of buildings following flooding. The standard of repair is defined as follows:
The standard of repair is the extent to which repair work is carried out and the extent of measures undertaken so that damage from future flooding is minimised. The standards of repair are determined through risk assessment. The flood resilience or flood resistance meas-ures in the standard of repair can include dry-proofing and wet-proofing of the property.
Three standards of repair are defined in this book (see Chapter 4) and relate to the level of risk determined (see Chapter 3). They can be summarised as follows.
1 Standard of Repair Level A. The risk assessment shows that there is little or no
risk of a future flood. It is recommended to repair the building to the original specification, although some minor upgrades may be incorporated to improve the flood resilience.
2 Standard of Repair Level B. The risk assessment shows that the likelihood of a
future flood is low to medium, ie it is considered sufficiently high to recommend repairs to increase the resilience and/or resistance of the property above the original specification.
3 Standard of Repair Level C. The risk assessment shows that the risk of a future
flood is high. It is recommended to instigate repairs that will increase the resilience and resistance of the property significantly. Such repairs involve dry-proofing and/or wet-proofing of the building.
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Several parties have direct roles and responsibilities with regard to flooding in the United Kingdom, the main legislative and regulatory organisations involved being listed below.
1 Government. This includes the Department of Environment, Food and Rural
Affairs (Defra) and the devolved administrations, which are responsible for national policy and providing strategic guidance on flood management. The Office of the Deputy Prime Minister (ODPM) and devolved administrations provide the policy and guidance on planning and flood risk relating to development.
2 Regulators. The Environment Agency manages flood risk in England and Wales,
while the Scottish Environment Protection Agency (SEPA) has the same role in Scotland. Each provides a 24-hour flood warning service and an emergency response service. They maintain and improve main rivers for the efficient passage of flood flow and the effective management of flow. Along with other operating authorities, the Environment Agency also builds and maintains flood defence structures where appropriate to reduce the probability of a flood event occurring. It also issues licences for the abstraction of water, impounding of watercourses and discharges of effluent to controlled waters. In England and Wales local authorities are responsible for non-main rivers, although the Environment Agency has a supervisory role over them and can make recommendations to the local authorities.
3 Local authorities. Councils are the operating authorities for ordinary watercourses.
They are the planning authorities responsible for implementing planning policy guidance from government. Through planning controls, councils seek to reduce flood risk by minimising development in flood risk areas.
4 Water companies. These companies are responsible for the supply of clean water
and the treatment and disposal of sewage. They are responsible for public sewers and the maintenance and function of this infrastructure. (Private drains, pipes and sewers are the concern and responsibility of property-owners, local authorities and insurance companies. Public sewers are the sole responsibility of the sewerage undertaker – usually the local water company. All repairs to public sewers should therefore be referred to the water company.)
5 Internal drainage boards. In defined areas the drainage boards have operational
and regulatory powers on specific watercourses. They operate and improve flood defences and provide emergency response.
6 Ofwat. The Office of Water Services (Ofwat) is the economic regulator for water
and sewerage services in England and Wales. It is a non-ministerial government department led by the Director General of Water Services. Ofwat works with the Government, the Welsh Assembly Government and the quality regulators (the Environment Agency, the Drinking Water Inspectorate, English Nature and the Countryside Council for Wales) to monitor the way in which water companies provide a good-quality, efficient service at a fair price.
7 WaterVoice. This organisation operates through nine regional committees in
England and a committee for Wales. It represents the interests of customers in respect of price, service and value for money; it also investigates complaints from customers about their water company.
During the repair process, the company providing insurance for the building will also have a key role to play.
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This guide provides advice for each of the steps that make up the process of repairing and, where necessary, improving the flood resilience and resistance of buildings after a flood. The recommended process is summarised in Figure 1.3. More detailed flow charts are included in the chapters to illustrate specific steps.
When determining and undertaking repairs it is important to consider all the steps, in the right chronological order, regardless of the severity of the flooding.
Throughout the guide, readers are referred to specialists for advice where necessary. Appendix 1 provides contact details for organisations, while more advice on specific topics can be obtained from the sources listed in Appendix 8 References and Appendix 9 Further reading.
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The guide is intended for use by professionals within the construction industry who are directly involved in any of the stages of the repair work. General builders, surveyors and members of the public may also find the guide useful in the reinstatement of flood-damaged properties. For the public, the advice may serve as guidance when managing relationships with contractors undertaking work.
The guide may also be used by owners of properties that have been flooded, or that are at risk of flooding, to identify suitable options for reducing the risk of damage from future floods. The building-owner will have considerable input into standard of repair
decisions (see Section 3.2), but they will seldom have the technical expertise to specify repairs in full. Therefore, it is essential that they consult with construction and insurance professionals.
Non-professionals using this guide need to remember that assessments should always be carried out by suitably qualified and experienced professionals.
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Guidance is provided for repair of the most common types of domestic building in existence in the UK and covers the main elements that are likely to be affected by floods, including basements, floors, walls, windows, doors and services. The recommended repairs are written for buildings that have suffered a flood event, although some of the advice may be applied in anticipation of a future flood event.
It is generally recognised that flood depths of greater than 1 m can result in damage to the structural integrity of a building. Such issues are not covered by this guide, which is intended for floods below 1 m height. The advice is applicable to flooding from a variety of sources (see Section 1.1).
The guide is structured to follow the chronological order of the repair process. It includes information on:
making safe, decontamination and drying of buildings (Chapter 2), including ways to measure moisture content and how to assess whether or not a building has dried sufficiently for repairs to be undertaken
post-flood surveys and risk assessments (Chapter 3), to determine the scope of the repair work required and guide the standard of repair to be implemented standards of repair (Chapter 4) including the use of flood protection products,
although detailed guidance on different products is not within the scope. Although some of the guidance may be applicable to historic buildings, it is strongly recommended that, before undertaking any work on such buildings, specialist advice be obtained from heritage organisations such as English Heritage, Cadw, Historic Scotland and the Society for the Preservation of Ancient Buildings; see Appendix 1 for contact details. Historic and older buildings are often particularly susceptible to the impact of floodwater, yet preservation of the original structure often means that there is limited potential for increasing its flood resistance. Consultation with the appropriate authorities may also be required where legal protection applies – for example, listed buildings or those in conservation areas.
O
Ouutt ooff ssccooppee
The guide does not cover administrative arrangements in Northern Ireland, which differ from those in England, Scotland and Wales, although the technical principles contained within the guidance remain consistent and are applicable for buildings in Northern Ireland following flooding.
The guide does not cover the repair of major structural damage that can result from severe flood events. Nor does it consider damage to foundations, as this has structural implications for the building. Seek specialist advice on these issues.
The guide also excludes flooding caused by leaks from plumbing (water services, drainage systems or household appliances) and flood damage caused by rainwater leakage into buildings, eg through defective roofs and gutters. Some elements of the guide may be useful in these circumstances (for example decontamination and drying, which are directly applicable), but they are not written specifically for such incidents. The advice does not include information on wet-proofing opportunities that can be incorporated within initial building design, eg designing kitchens to include moveable appliances (rather than permanently fixed units) so that they can be moved to safe locations if a flood warning is given.
Specific requirements for prefabricated buildings are not included. For these, the system supplier should provide advice on flood resilience, flood resistance and repair.
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Provision of guidance on flooding, flood risk and flood repair is an important part of CIRIA’s ongoing research. More information (including a series of downloadable advice sheets) can be found on CIRIA’s flooding website at <www.ciria.org/flooding/>.
The following CIRIA documents are available:
B14 Design of flood storage reservoirs (Hall et al, 1993)
C506 Low-cost options for prevention of flooding from sewers (May et al, 1998) C521 Sustainable urban drainage systems – design manual for Scotland and Northern
Ireland (P Martin et al, 2000)
C522 Sustainable urban drainage systems – design manual for England and Wales (Martin
et al, 2000)
C523 Sustainable urban drainage systems – best practice manual for England, Scotland,
Wales and Northern Ireland (Martin et al, 2001)
C599CDSUDS compilation CD (Martin et al, 2004)
C609 Sustainable drainage systems. Hydraulic, structural and water quality advice (Wilson
et al, 2004)
C624 Development and flood risk – guidance for the construction industry (Lancaster et al, 2004)
C625 Model agreements for sustainable water management systems. Model agreements for
SUDS (Shaffer et al, 2004)
C630 Sustainable water management in land use planning (Samuels et al, 2005)
C635 Designing for exceedance in urban drainage systems – good practice (Balmforth et al, 2005)
C638 Climate change risks in building – an introduction (Vivian et al, 2005)
FR/IP/45 Reducing the impacts of flooding – extemporary measures (Elliott and Leggett, 2002).
There is also a series of pamphlets jointly produced by the Environment Agency and CIRIA:
After a flood. How to restore your home (CIRIA and EA, 2001a)
Damage limitation. How to make your home flood resistant (CIRIA and EA, 2001b)
Flood products. Using flood protection produces – a guide for homeowners (CIRIA and EA,
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Fiigguurree 11..33 Recommended repair process for a flooded building
Carry out repairs to the chosen standard
(Chapter 4) Supporting information on
typical building elements (Appendix 8 References
and Appendix 9 Further
reading)
Advice on making a claim and appointing surveyors
and contractors (Appendix 3) Supporting information on
typical building elements (Appendix 8 References
and Appendix 9 Further
reading)
Advice on making a claim and appointing surveyors
and contractors (Appendix 3) Further infortmation on dehumidification
(Appendix 4) Seek specialist advice for
historic buildings
Undertake a post-flood survey for material
and structural damage (Chapter 3)
Complete the post-flood risk assessment to inform requirements for standards of repair
(SoR) (Chapter 3) Determine the standards of repair required for the building (Chapters 3 and 4)
Undertake the drying of the building
(Chapter 2) Decontaminate the
building (Chapter 2)
Make safe the building for further work, complete a health
and safety risk assessment (Chapter 2)
Be familiar with flooding causes and use
of the guide. Document causes and extent of
flooding (Chapter 1)
Advice on making a claim and appointing surveyors and contractors (A3) and Organisations that can advise on flooding (A1) Contact the insurance
company
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Making safe, decontamination and drying should be undertaken as soon as possible after the floodwater recedes and before the post-flood survey (see Chapter 3). Floodwaters can bring both the structure and contents of a property into contact with silt, debris and other contaminants. It is likely that the building fabric will absorb moisture, the degree of saturation being dependent upon the duration of the flood. Although it is desirable to reduce the moisture content in all locations as quickly as possible, the process needs to be carefully controlled to avoid making the situation worse. Particular care should be taken to gain the necessary prior permissions and to employ appropriate techniques when working with listed or heritage properties. Figure 2.1 shows the process of making safe, decontaminating and drying a structure that has been flooded. It is important to complete the decontamination before starting the drying process. The information provided in this section is not exhaustive and further guidance can be obtained from property damage restoration specialists (see Appendix 1).
The flood-related damage needs to be documented before decontamination and drying takes place. The documentation, which may include written records and digital photographs, can be used to determine the standards of repair required and is normally required by insurance companies as part of the loss adjustor and contractor relationship. Activities related to making safe, decontamination and drying, as well as the amount of damage involved, should all be documented.
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A competent person should carry out a full health and safety risk assessment for the making safe, decontamination and drying work before these activities are started. Failure to identify problems and make the building safe may endanger the health and safety of those involved in decontaminating and drying the property. The making safe process should be iterative with decontamination and drying, because, as
decontamination progresses, it may become apparent that further elements need to be made safe before work can continue.
For any work to be undertaken during decontamination, drying, survey or repair, a method statement should be prepared. This should cover the methods to be employed and the means of protecting the personnel involved. The British Damage Management Association (BDMA) has developed a risk-based approach for this, which is provided in Appendix 2. Alternative means of assessing the health and safety risks may be used, but they should cover as a minimum requirement the issues in Appendix 2.
The making-safe process includes:
checking that the flood has receded and there is no immediate danger of it recurring identifying the full range of potential contamination sources and types.
Contaminants carried in floodwater may have been diluted but can still be hazardous. Washing and sanitisation can reduce the hazard. Potential local sources of contamination must be considered, eg industrial or agricultural sources, fuel tanks or sewerage systems. Use proper chemical analysis to determine the nature of the contamination where necessary
identifying any building issues, such as structural stability (of both the building and its surrounds), gas and electrical safety, and slip and trip hazards. For help in assessing structural integrity, the Institution of Structural Engineers provides listings of qualified structural engineers. The Royal Institution of Chartered Surveyors and the Association of Building Engineers can also provide advice (see Appendices 1 and 3)
switching off all utilities and services that enter the building to reduce the risk
they may pose until specialists can check their integrity.
A booklet for building-owners, After a flood. How to restore your home (CIRIA and EA, 2001a), provides further information on making the building safe.
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Fiigguurree 22..11 Method for safe and effective decontamination and drying of a flooded building
Individuals carrying out the making safe, decontamination or drying work should fully understand the health and safety requirements, in particular the importance of personal hygiene and use of appropriate personal protective equipment.
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Flood events can damage people’s health and on occasions result in loss of life. This can result from direct or indirect effects, as follows:
direct – those happening during or immediately after the flood;
indirect – those developing in the days or weeks following the flood and
longer-term effects, appearing after months or years.
Conduct a full health and safety risk assessment
(Section 2.1)
Assess flood damage to the building contents and manage as appropriate
(Section 2.1.5)
Decontaminate the building in accordance with the guidance
(Section 2.2, Table 2.2)
Dry the building until the moisture content of materials reaches an appropriate level
(Section 2.3, Table 2.2)
Fully document the making safe, decontamination and drying activities and proceed to post-flood
survey of the building (Chapter 3)
Decide method for disposal of remaining standing water and extract the bulk of the water
(Section 2.1.4)
Be aware of the direct and indirect health effects of flooding
(Section 2.1, Table 2.1)
Direct health effects include the following.
1 Death by drowning, heart attacks, strokes, hypothermia and accidents. The number
of deaths associated with flooding is strongly related to the life-threatening characteristics of floods (rapidly rising water, deep floodwaters, objects carried by the fast-flowing water) and the behaviour of the victims.
2 Injuries (sprains, strains, lacerations, contusions etc). These are likely to occur in
the aftermath of a flood as people return to their homes to begin cleaning up. Indirect health effects include the following.
1 Infectious diseases (gastrointestinal diseases, dermatitis, conjunctivitis) and some
rare cases of vector-borne diseases. Infectious diseases typically are confined to illnesses endemic to the flooded region. The risk of introducing new diseases, such as vector-borne, may be low, but there may be an increase in spread of any diseases that were present before flooding. Sanitation problems or overcrowding among temporarily displaced persons will increase the risk.
2 Poisoning caused by the rupture of underground pipelines, dislocation of storage
tanks, wash-off from agricultural land, runoff from toxic waste sites, or release of chemicals stored at ground level.
3 Stress caused directly by the flood, the experience of a flood and dealing with its
aftermath.
4 Post-traumatic stress disorder, including anxiety and depression, and psychological
disturbances. Apart from the trauma caused by flooding itself, many mental health problems stem from geographical displacement, damage to the home or loss of familiar possessions. Lack of insurance adds to the stress levels and particularly affects low income families that may not be able to afford insurance. Such problems may continue for months or even years after the event itself. A link between psychological stress and physical illness after flooding has been determined in a study after a major flood in October 2000 (Reacher et al, 2004). Practical support to flood victims is of particular importance after a flood event. Organisations such as the Samaritans and the Red Cross provide support to individuals suffering as a result of a flood. Training in support of flood victims would allow loss adjusters and damage restoration specialists to understand the needs and vulnerability of victims. There is a high cost associated with stress and failed relationships that cannot be recovered through insurance. The support provided by families, authorities, professionals and voluntary services is essential to avoiding much of the stress and its consequences after a flood.
Table 2.1 summarises direct and indirect health effects of the flooding of buildings.
Anyone suffering (or who is concerned that they may be suffering) either direct or indirect health effects as a result of flooding should seek professional medical assistance at the earliest opportunity.
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Moulds can grow and present hazards in the aftermath of a flood. In extreme situations they can appear within 48 hours, so it is essential to proceed rapidly with decontamination and drying (see also Section 2.3.4). Dry rot of timber is a risk if timbers are not properly dried out (see also Section 2.3).
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Fast-flowing floodwaters can affect foundations through scour action on the surrounding earth, thereby exposing or undermining the structure. Additionally, some soils can slump and settle following a flood, producing structural movements in the foundations. A visual inspection of the perimeter of the building will usually indicate whether the foundations have been affected. Where slumping or settlement is identified, specialist advice should be obtained to determine the need for remedial activity. Note that settlement can occur over long periods of time.
Sloping sites can be subject to slumping when they are affected by floodwater. This results in destabilisation or movement of the foundations of the building. Often, this causes major structural damage that can only be corrected with guidance from a structural engineer. Peat-covered slopes are particularly vulnerable in this respect. This guidance does not specifically cover the repair of flood-damaged foundations, so further specialist advice should be sought, as it is important to know the condition of the foundations after a flood.
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Remove standing water first. Often this can be pumped into the local foul sewer, subject to serviceability and approval by the sewerage undertaker. Other specialist methods may have to be considered involving intermediate bulk containment or use of vehicle-mounted wastewater tankers. The chosen method of disposal must comply with the Control of Pollution Act 1989 and the Controlled Waste Regulations 1991.
The following issues need to be considered in pumping water.
If it is safe to do so, start pumping water from the basement. There is no need to wait for insurance approval so long as guidance from a specialist has been given and is being followed. In practice there are rarely problems with removing water from basements, but care is always required; further guidance is available (CIRIA and EA, 2001a). Qualified and experienced professionals should be employed to undertake pumping work. Records should be maintained of the flood event, for example photographs of the flood damage and recorded heights of water, to aid future repair work and for insurance purposes.
Before beginning detailed investigations or work in flooded basements it is essential to identify and deal with potential safety hazards.
Water should be removed, in a controlled manner, over a period of several days until all of the floodwater has gone, as serious structural damage can result if the water is removed too quickly. It may take up to a week to remove the floodwater.
Remove no more than 1 m depth of floodwater in any one day.
Vigilance is needed during dewatering to identify signs of structural movement or damage while the pressure of the floodwater is being reduced. NOTE: removal of water may reduce the floodwater level in adjacent basements too.
After drainage, water may continue to pond on the basement floor. This can be a sign that the tanking has been damaged in some way during the flood. The basements of older buildings may not have had tanking or waterproofing treatments, relying instead on the protection afforded by water-resistant building materials (eg slate). If the basement is no longer sufficiently water-resistant, tanking or waterproofing may have to be installed during repairs (see Section 4.17).
Contamination in basements following floods may result in air quality problems. This is a serious safety issue that must be appropriately addressed before work starts. Air quality may be poor and require forced ventilation to dissipate fumes or pollutants. In areas where coal mining has been carried out, gas escaping from the mines can be driven to the surface following flooding and this can pose a health and safety risk.
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Taabbllee 22..11 Direct and indirect health effects
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Where possible, damaged building contents should be removed to ensure that decontamination and drying activities can take place unhindered (see also Section 2.2.1). Undamaged contents should be salvaged and moved to an unaffected area for storage.
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Riisskk ffaaccttoorrss HHeeaalltthh eeffffeeccttss
D
Diirreecctt hheeaalltthh eeffffeeccttss
Stream flow velocity Topographical features Absence of warning Rapid speed of flood onset Deep floodwaters
Rapidly flowing waters carrying debris Pre-existing health/mobility problems Failure of natural or artificial protective structures by overtopping or collapse Dam failure
Standing water Contact with water Contact with polluted water Missing manhole covers
Risk of injury and drowning
Risk of respiratory diseases, shock, hypothermia and cardiac arrest
Risk of wound infections, conjunctivitis, dermatitis, gastrointestinal illness, and ear, nose and throat infections
Falls leading to head injuries, broken limbs or cuts and bruises
IInnddiirreecctt hheeaalltthh eeffffeeccttss
Damage to water supply systems
Damage to sewerage and sewage disposal systems
Damage to gas and electrical services Insufficient supply of water for water or washing Loss of wastewater services
Disruption of underground piping Dislodgement of storage tanks Overflow of toxic waste sites
Release of chemicals including general household chemicals
Disruption of petrol storage tanks, including fire risk
External pollution factors (eg oil tanks, petrol tanks, farm storage and land runoff) Heavy rainfall
Rodent migration
Clean-up activities following flooding and repair Cryptosporidium, in drinking water after a flood
Waterborne infections (eg enteropathogenic
E coli, shigellosis, hepatitis A, leptospirosis,
giardiasis, campylobacteriosis) Vector-borne diseases Rodent-borne diseases Dermatitis and conjunctivitis
Electrocution, injuries, lacerations and puncture wounds
Acute or chronic effects of chemical pollution Vapour inhalation
Stress and trauma, from work required to clean up housing and damage caused to property and belongings, removal from house or loss of pets or property
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Decontamination should begin as soon as possible after the flood recedes and preferably within 24 hours. It is important that anyone involved in decontaminating the building wears appropriate personal protective equipment (PPE); requirements for this should be determined in a health and safety risk assessment. Gloves, overalls, safety boots and eye protection will usually be needed. Further specialist equipment, such as breathing apparatus, should also be available where required.
Contamination may either be physical (sediment), biological or chemical, and the cleaning regime should reflect the type of contamination that is present. It should be assumed that floodwaters are contaminated with a mixture of pollutants, probably including sewage. Some pollutants – eg petrol or oil – may be readily identifiable visually or by the presence of an odour, but other contaminants may be less easy to identify without chemical analysis. The existence of industrial, agricultural or
commercial processes upstream of the flooding will help to determine the risk of other pollutant hazards being found in the floodwater. The source of the floodwater should be identified, as this will help to indicate which contaminants may be present. Where chemical or other industrial pollutants are suspected, floodwater samples should be collected using a clean specimen bottle for chemical analysis.
Care should be taken to consider the possibility of trapped or adsorbed contaminants in the building and to identify how they may be safely removed. Where necessary, building components, eg kitchen units, fixed cupboards, appliances or skirting boards, should be removed to expose areas for cleaning. Alternatively, access points can be opened up to allow cleaning; for example, small areas of floorboards could be lifted to allow access to the void space below (see Figure 2.2). See Table 2.2 for further advice on decontamination.
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Fiigguurree 22..22 Floor boards damaged and removed to allow for surveying
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For full decontamination of a building the following process is recommended.
1 Use a shovel or scoop to clear debris and silt. The disposal of debris, silt and other materials must be carried out in compliance with the Control of Pollution Act 1989 and the Controlled Waste Regulations 1991. Dispose of contaminated materials in an appropriate fashion, possibly as hazardous waste. Advice can be obtained from
specialist waste disposal companies, the local authority or regulators, such as the Environment Agency, SEPA and DoE NI. Remove sandbags, which frequently are contaminated with sewage.
2 Determine and document the contaminated areas within the building and identify the affected materials. Include materials visible on the outside and inside surfaces of the building and within building cavities and floor voids. Identify contamination through visual inspection, the presence of odours or analysis. Identify the source of the floodwater to assist in making these determinations (see Section 1.1).
3 Remove building contents from affected areas to enable the restoration of the building structure to proceed. Use the following approach:
store undamaged contents in an unaffected area
identify salvageable contents and take appropriate action to prevent further damage before restoration
remove unsalvageable contents for disposal once agreed with all interested parties (owners and insurers).
4 Wash down and clean affected walls, floors and basement areas using appropriate amounts of detergent. Use power washing or mechanical scrubbing, if possible without causing further damage. For minor floods, scrubbing by hand may be sufficient. Check the water supply is clean before beginning this work. (Detergents are wetting agents and may react with some paints and adhesives. Consequently, care should be taken to avoid excessive wetting during this process where possible.) 5 Detergents can be used to clean chemical or oil contamination. Where mould,
bacteria or fungi are present, use detergents and sanitising disinfectants to remove them effectively.
6 Always rinse down the whole area thoroughly with clean water after detergents have been applied.
7 If necessary, take swabs from surfaces for analysis to determine the effectiveness of the decontamination.
8 Apply further detergents or sanitising disinfectants to minimise the potential for mould and bacterial growth. Normally each area will have to be cleaned at least twice.
9 Document the activities undertaken for future reference in determining standards of repair.
If done properly, decontamination of a flooded building can be fully effective, especially where the contamination is restricted to accessible areas internally. However, there are some special circumstances in which it will be necessary to undertake further action, which are summarised below.
External walls may be contaminated, and it is important to decontaminate them (see Figure 2.3). The same type of cleaning process described above can remove contamination to these walls. For brick walls, refer to advice from the Brick Development Association (Harding and Smith, 2002).
Cavity walls, voids and floor voids need to be cleaned properly. They can be flooded with detergents and fogged with sanitising agents. If irrecoverably damaged, insulation in cavities and voids may need to be removed for decontamination. Floating floors, with insulation installed under a screed layer or surface, can
present particular difficulties. If the insulation is wetted by floodwater then it is difficult to decontaminate and dry, although special methods exist to dry in situ. If necessary remove the screed layer for decontamination.
Odours may be present after a flood. In general, they can be vented off, but if they originate from decaying materials then those materials will need to be decontaminated or removed.
Oil contamination, especially from storage tanks, can present a specific risk to building materials, since fuel oil released from the tanks can be absorbed into walls and floors. Once absorbed, it is difficult to remove and may necessitate plaster, plasterboard or render being stripped from walls to effect complete decontamination (see Figure 2.4). New enzyme-based products can be extremely effective on this type of contamination, but the use of specialist contractors is recommended. Basements and cellars are vulnerable in flood conditions, so decontamination is
often problematic. (Not only is there a risk of drowning in such confined spaces, but they may also contain toxic gases or vapours produced from floodwater-borne chemicals. The latter hazard is typically met with in cellars, but can pose a risk in any enclosed space where there is little or no ventilation. Gases and vapours may be toxic in their own right or may have displaced the air required for normal respiration.)
During a flood, water will generally flow fastest into the basement, carrying silt that then settles out. Extensive cleaning is often necessary to remove the silt. In particular, it is important to check that any ventilation ducts into the basement are properly cleaned and reinstated, and to clear silt from drainage forming part of the tanking system. NOTE: materials removed must be disposed of in accordance with the Control of Pollution Act 1989 and the Controlled Waste Regulations 1991.
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Fiigguurree 22..33 Flood damage to walls
F
